2x Composite Capture w/ PCIe

I'm trying to spec out a project right now where we need two channels of composite capture into Isadora on a Mac Pro. For latency reasons we would really like to go with PCIe but the machine has a pair of double width graphics cards in it which only leaves one slot for the PCIe capture card. Any suggestions for a single card that will give us two channels in one slot and that has been tested with Izzy?